Fabricius from the Noctuidae family) were abundant (10–20 larvae per plant during the mid- dle of the season, observation by YSY) in conventional cotton plots whereas they were scarcely observed in Btcotton plots. Nevertheless, previous studies did not detect any measurable dif- ference in parasitoid foraging between slightly-infested Bt and heavily-infested non-Bt plants from the perspective of changes in profile of organic volatile compounds (VOCs) [ 53 – 56 ]. Besides the effects of plant-emitted volatiles, other possible mechanisms underlying the low density of parasitoids in Btcotton field deserves further research. Without replication of con- ventional and Btcotton crops (fields) in our study, it is possible that differences in parasitoid numbers resulted from other factors, such as local landscape features. The meta-analysis by Chaplin-Kramer et al.[ 57 ] has shown that landscape features on a narrower spatial scale is more likely to influence specialist natural enemies (e.g. aphid parasitoids), whereas generalist predators responded more strongly to landscape features at broader scales. In such a small- scale landscape in our study, we assume that the difference in parasitoid abundance between the conventional and Btcotton crops might behave slightly differently in other fields showing different landscape features.
It turned out that the expression of the Cry 1A gene substantially varied between genetic backgrounds and between two subsequent years for a few of these varieties. The efficacy of pest-resistance is confirmed but its level is not perfect, the mortalities of the H. armigera larvae in indoor and furthermore in outdoor bioassays are not always sufficiently high. This is consistent with the acknowledgement that the pest-resistance of Bt-cotton in the Yangtze River Valley is not so good, notably with reference to the Yellow River Valley. We suggest that this relatively lower efficacy could result from the transplantation technique which induces stresses to the cotton plant growth and development. We believe also that it is an indirect effect of the widespread use of hybrid varieties for which it is quite difficult to achieve pure enough hybrid seeds containing the Bt-gene.
galling and egg mass index compared with its isoline and this may be because isoline permitted penetration of infective juveniles and development of feeding sites but the nematodes did not develop into adult females resulting in a reduction of RKN reproduction (Jenkins et al., 1995). The high RKN reproduction in Btcotton as shown by the galling index reduced cotton growth resulting in shorter plants which also weighed less than the isoline treatment. Hao et al. (2009) similarly reported that plant height and weight were negatively correlated with the galling index. Shoot weight of inoculated lettuce was reduced up 32% after infection with M. hapla (Wong and Mai, 1973).
Keywords: Bt crop, nontarget pest, ecological effect, pest status evolution, pest management, mirid bug, aphid.
The adoption of Bt (Bacillus thuringiensis) crops has improved crop yield, reduced chemical insecticide use and induced an increase in farmer profits; however, some concerns persist about their potential environmental risks, including the impact on nontarget arthropods (Romeis et al., 2008). In China, Btcotton was first grown commercially in 1997. As the levels of cultivated Btcotton increased, populations of the target pest Helicoverpa armigera were found to have substantially declined (Wu et al., 2008). In addition, reduced insecticide use in Btcotton has shown positive side effects, such as increased pest biocontrol services provided by natural enemies (Lu et al., 2012), but also negative side effects, such as mirid bug outbreaks (Lu et al., 2010). How this shift in pest status may impact interspecific arthropod interactions in Btcotton needs to be further investigated (Hagenbucher et al., 2013; Zeilinger et al., 2011; Zhang et al., 2018). Mirid bug feeding often causes tattered leaves on host plants, suggesting that interspecific competition with other leaf- feeding insects may occur. Furthermore, mirid bugs may also prey on the cotton aphid Aphis gossypii and other arthropod pests (Jiang et al., 2015). Hence, mirid bugs have the potential to act as arthropod biocontrol agents during their outbreaks.
The model parameters employed in this study are based on the tobacco budworm Heliothis virescens (Lepidoptera: Noctuidae), a key pest of cotton crops. The standard error r 2 of migration is estimated as 4 km (Korman et al., 1993). The initial frequency of the resistance allele fs0 is assumed to be 0.0015 (Gould et al., 1997). The varieties of Btcotton currently available are highly toxic to tobacco budworm larvae (Gianessi & Carpenter, 1999) and the recent determination of the molecular basis of BtCry1Ac resistance (Gahan et al., 2001) is consistent with resistance being recessive, as observed in bioassays (Gould et al., 1995). A ‘high dose’ strategy, killing more than 97% of heterozygotes and susceptible homozygotes (s ¼ 1.00 and hs ¼ 0.95) is used in most simulations. We also studied a ‘middle dose’ strategy (s ¼ 0.80) and a ‘low dose’ strategy (s ¼ 0.60). We assumed that the genotype toxin dose–mortality curves for insect larvae are such that the functional recessivity of resistance (h s ) is not affected by the amount of toxin produced by transgenic plants. An acute, recessive cost of resistance has already been observed in the laboratory for some strains of H. virescens (F. Gould, personal communication). In the absence of quantitative data, for the main simulations we fixed the cost of resistance c to 0.15 and its level of dominance h c to 0.20. Genotypic survival for the three strategies is summarized in Table 1.
Landscape complexity affects population dynamics of both pests and their natural enemies ( Aviron et al., 2016; Meisner et al., 2016; Vasseur et al., 2013 ). For instance, pest densities tend to be lower when the proportion of semi-natural habitats in the landscape increases, especially because it increases natural enemies' spillover into crops ( Inclán et al., 2015; Veres et al., 2013 ). Source-sink dispersal of pests and their natural enemies also occurs from crop to crop due to the spatial and temporal heterogeneity of cropping areas (i.e., crop planting, harvesting, and removal of residues), with important consequences for pest management strategies ( Carrière et al., 2006; Schneider et al., 2015; Venugopal et al., 2015; Vialatte et al., 2006 ). In source crops, arthropod populations have positive growth rates, while in sink crops, they tend to have negative growth rates, but do not go extinct thanks to the arrival of excess individuals from neighbouring source patches ( Holt, 1985; Dias, 1996; Hanski, 1999; Holyoak, Leibold & Holt, 2005 ). The role of specific crops as a source or sink of pests is also dynamic on a longer term and may be altered by wide- scale adoptions of particular agricultural and landscape management practices ( Zeilinger et al., 2016 ). This is the case of cotton crops in China, that have changed from sinks to sources of pests. Indeed, the wide-scale use of Btcotton and the correlated decrease in insecticide use have lead to important outbreaks of mirid bugs in Btcotton fields, eventually becoming new pests ( Lu et al., 2012a, 2010a; Lu & Wu, 2011 ). In addition, mirid bugs develop well on cotton resources, especially when flower resources are available (i.e., from July to August; Dong et al. 2013 ). However, the contextual source or sink role of specific crops, as well as arthropod movements in multi- crop landscapes is poorly understood.
cotton varieties in connection with the farmer structures, their command in the chemical control with reference to the Btcotton use. The survey covered six villages from the five important districts in the cotton production areas of the province, which includes 208 households in 2002 and 2003, among them there were only 39 households using non-Btcotton varieties. Sampling methods were used during survey are as follows: firstly, we chose Feixiang, Guangzong, Shenzhou and Hejian counties from typical cotton production regions. And secondly, we chose typical village from every county and chose smallholders at random from the villages. We assure the number of valid questionnaires is not less than 20 in each and every village. The survey in 2003 was cinducted again by using the same survey questionnaire that in year 2002; in other words, we had the same group of smallholders surveyed during two years, so as to ensure continuity of the survey and to capture eventual changes of farmers' practices or opinions meanwhile. In the agricultural system, the household selected one or several livelihood strategies depending on the natural, physical, financial, human and social capital. In Hebei Province, agriculture is the main source income for the household, especially comes from planting. In the main crops, the income from cotton is the main source. Therefore, using the canonical correlation analysis to analyze the relationship between cotton income and the consumption expenditure of the household and deeply explain the extend impact of the cotton and the influencing factors.
gifuensis (9%) whereas in 2013, only Trioxys spp. was observed (100%). At late growth stage of the cotton crop,
100% Trioxys spp. were recorded only in 2013. Discussion
The differences in the population density of cotton aphid recorded in different exclusion cages showed a strong top-down impact of natural enemies over three growing seasons from 2011–2013. The numbers of aphid remained low from middle June to early July (early to middle plant growth stage of the crop). In open cotton field survey, population dynamics of aphids varied with the seasons and stages of plant growth where the highest population density of cotton aphid was recorded during 2012, and at the middle plant growth stage (July) over three growing season. More specifically, early and middle growth stages of cotton crop are the most critical for aphid infestation as a sudden increase in the density could be observed. Among the natural enemy guild, the most common species recorded were coccinellids, spiders, and aphidiine parasitoids in three sampling seasons where the highest numbers of natural enemy was recorded at middle plant growth stages of the cotton crop (see Table 2). Potential aphid parasitoids were identified as Trioxys spp. and Aphidius gifuensis A. during two sam- pling season (2012 and 2013). Overall, these results suggest that natural enemy populations should be conserved by avoiding insecticide application at early plant growth stage of cotton crop that would ultimately suppress the increasing numbers of cotton aphid populations at middle and late planting growth stages. Moreover, this series of experiments is very useful information to highlight and provide a direct assessment of the seasonal importance of different natural enemy groups attacking cotton aphid in the Btcotton ecosystem along YRR of Northern China.
Four different degrees of predator exclusion were tested using various exclusion designs in the Btcotton field: (i) Exclusion cages with 5306530 m m openings in which aphids were fully protected from all insect natural enemies. (ii) Restriction cages with 363 mm openings in which aphids were partially protected. This size of openings restricted entry by large predators i.e. Coccinellids, but allowed small predators to enter [13,27]. (iii) Sham cages built with 5306530 m m mesh netting but included a 40 cm high opening in the middle and the bottom respectively (modified from ). This treatment was used to assess possible disruptive effect of caging (e.g. mesh, wood sticks, etc.) on the activity of natural enemies and aphid population growth within the plots. (iv) No cage, a completely open area (named ‘‘open field’’ hereafter), which used four wood sticks standing upright into the ground and a tape surrounding them as guidance for sampling range and plot size and position.
Lu S, Tian X and Zhang R, Need to further address the issue of cotton quality (in Chinese). In Proceedings 'Chinese Cotton Research Conference', Baoding,
Hebei: Chinese Cotton Publications, 2006. 56-58.
Pemsl D, Waibel H and Gutierrez AP, Why do some Bt-cotton farmers in China continue to use high levels of pesticides. International Journal of
Helicoverpa zea yes perhaps no no
3.2. Persistence of the chemical pathway to control Bt-cotton target pests
First of all, it is important to remember that the emergence of bollworm resistance to pyrethroid- based insecticides was one of the reasons for proposing transgenic cotton. Musser et al. (2010) reported on the monitoring of bollworm resistance to pyrethroid insecticides in nine cotton States— Texas, Mississippi, Georgia, Tennessee, South Carolina, Louisiana, Arizona, Missouri and Virginia. Resistance is monitored by the Vial-test, which consists in collecting target pests, enclosing them in a tube impregnated with 5 µg of pyrethroid, and recording the survival rate. For the 2007-2009 period, the bollworm survival rate reached 10 to 30% in seven of the nine States, showing persisting resistance to pyrethroids, even though the insecticides have been used much less since Bt-cotton has been grown. Although they could not give any reasons for this, the authors of the paper pointed out that the rate was even greater than that measured in 1998. This work is therefore truly relevant at a time when a return to conventional cotton growing is being mooted.
Mots clés : biotechnologies / pratiques culturales / rentabilité / différenciation des exploitations / OGM
Abstract – Differentiated early performance of Btcotton: Case in Burkina Faso. The economic beneﬁt
of transgenic crops for producers in developing countries remains a matter of concern and controversy. Only a few studies have taken into account differences between producers to understand the variable effects of transgenic crops, particularly in the case of Btcotton incorporating Bacillus thuringiensis genes for resistance to certain cotton pests. Our assessment study deals with Burkina Faso where the large-scale release of Btcotton occurred in 2009, and was then suspended in 2016. It addresses the cultivation practices of producers, in farms differentiated by their level of ox-drawn equipment, on the ﬁrst year of Btcotton large adoption and dissemination of recommendations for an adapted insecticide protection. We found that Btcotton increased yields, but to a lesser extent than expected; moreover, an increase in pro ﬁtability was only observed in farms with a good ox-drawn equipment (the healthiest ones), but not for the others representing 58% of all farms. This is the result of worst-off producers ’ strategies, consisting in reducing cash expenses in fertilizers and insecticide, which were further exacerbated by the high price of Bt cottonseeds. The case study points out that the early impacts of a new technology depend on its price and on taking into account, or not, the behaviour of the poorest producers.
About ten countries have adopted Bt-cotton since its commercial release in the USA in 1996. This release led immediately to concern about Monsanto’s monopoly and the loss of varietal diversity in adopting countries. There are very few studies addressing the actual state of the markets of cotton varieties in the adopting countries. This article pro- poses an analysis of such markets in China along with what is observed in other coun- tries where Bt-cotton is grown. Monsanto’s monopoly in supplying Bt-genes, indeed encountered in all countries except China, must be distinguished from a monopoly of Monsanto’s varieties. The latter monopoly is not always confirmed, and specifically not in China. In this country very active competition has taken place with a tendency for breeders to propose varieties integrating both Bt and hybrid F1 traits. Furthermore, com- petition has become excessive and implies negative effects to producers as well as to breeding and seed distribution companies, hence forcing the Chinese government to engage in regulation policies.
This yield gain took place prior to the Bt-cotton introduction, thanks to various intensification techniques at farmers' level. Cotton producers make use of various chemical inputs. In addition to the high level of fertilizing based upon mineral fertilizers and of chemical control of cotton pest, farmers systematically apply growth regulators and frequently install cotton plants on plastic mulch. In their yield maximisation approach, farmers also invest strongly in labour: they often eliminate vegetative branches and, during the fruiting stage they top cotton plants to enhance the boll growth. This brief description demonstrates the amount of technologies carried out and passed to farmers; this particular situation has seldom been
A number of studies have assessed the effectiveness and profitability of the use of Genetically Modified Varieties (GMV) in agriculture (Edens, et al., 1998; Marra, et al., 2003; McBride and Books, 2000). Genetically Modified Cotton (GMC) has received most attention to date, in particular insect-resistant varieties utilising a Bt gene (Bt-cotton). The relevance of using GMVs in developing countries nevertheless remains a matter of controversy. Even though most research studies in DC have shown a range of benefits accruing to smallholders some opponents ague that these varieties do not fit the real needs of smallholders in DCs (Mazoyer, 2000; Myers, 1999), others still question their effectiveness and profitability (de Grassi, 2003) owing to the high seed cost and even more so when seeds are supplied through a monopolistic market scheme (Pschorn-Strauss, 2004). After about ten years of dissemination of Bt-cotton, positive global impacts are still emphasized (Brookes and Barfoot, 2006; Gomez-Barbero and Rodriguez-Cerezo, 2006), but recently more balanced views also caution against shortfalls of the economic analysis implemented (Fok, 2006; Smale, et al., 2006) and focus more on the variation of the impacts according to local agronomic and institutional conditions (Fok, 2006; Smale, et al., 2006) or in advocating for organisational and institutional adjustments so as to ensure fair and profitable conditions to producers in DCs (Fok, 2006).
Mots clés : biotechnologie végétale / évaluation d’impact / transformation génétique / variétés / revenu
Abstract – Financial impacts of Bt-cotton on cotton companies and producers in Burkina Faso. Since 2008, Burkina Faso has been using Bt-cotton through engineered African varieties. The study – covering the 2008–2013 period – is a ﬁrst ex post assessment of the ﬁnancial impacts for cotton companies on the one hand, and producers taken on the whole, on the other hand. The study is original in taking into account the imperfect engineering of the varieties used. Impacts were assessed for a real situation of Bt-cotton use compared to a reference situation with no Bt-cotton use. Impacts were also evaluated in comparison to the scenario expected when a decision to adopt was made, for which the assumed 30% yield increase did not come about. Impacts were evaluated by the partial budget method, considering susceptibility to three criteria in industrial, commercial and world price areas. For farmers, the ﬁnancial impact was positive, although the pro ﬁtability rate of the extra cost of Bt cottonseeds was barely acceptable. For cotton companies, impacts were modest and became negative when world price dropped from its historic high as a result of ﬁber production shortfalls, ﬁber length decreases and discount at export sales. The commercial image of a country usually supplying quality cotton was negatively affected. The adoption of Bt-cotton in Burkina Faso is a rare case of technological evolution implying diverging impacts to the two main types of players. Potentially, this outcome could hurt the funding mechanism of research for further technical change.
This article analyses the process of liberalisation and regulation of varieties and seed markets in China through the specific case of Bt-cotton. The development of the mar- kets addressed is linked to the intellectual property protection as specified by the WTO, an organisation China joined in 2001. The Chinese institutional framework is studied here with the purpose of assessing the extent of its specificity relatively to other emer- ging countries which are also WTO member countries and which have also adopted Bt-cotton (namely South Africa, India and Brazil). The Chinese case reveals a clear example of excessive competition that no emerging countries had thought about pre- venting in their sui generis systems. China has recently opted for an administrative approach to cope with the varieties and seed “markets disorder” resulting from this excessive competition. By so doing, China violates some of the measures of its sui generis system although there is little chance of the regulation modalities being effective. Key words: China; cotton; intellectual property rights; regulation; seeds; varieties. Subjects: processing, marketing; vegetal productions.
Liberalization and regulation of variety and seed markets: the Bt-cotton case in China and in emerging countries
This article analyses the process of liberalisation and regulation of variety and seed markets in China through the specific case of Bt-cotton. The development of the markets addressed is linked to the intellectual property protection specified at the establishment of WTO that China joined in 2001. The Chinese institutional framework is studied here with the purpose of assessing the extent of its specificity relatively to other emerging countries, WTO member countries, and which also have adopted Bt-cotton (namely South Africa, India and Brazil). The Chinese case explored reveals a case of excessive competition that no emerging countries had thought about preventing in their sui generis systems. China has opted recently for an administrative approach to cope with the variety and seed "markets disorder", resulting from an excessive competition. By doing so, China violates a few measures of its sui generis system while the regulation modalities could hardly be effective.